symmetrical combination of films
对称组合膜系

• astrograph
• astrographic objective
• astrolabe
• astrometer
• Astrometry
• astronaut
• astronautics
• astronavigation
• astronomer
• astronomic
• astronomical aberration
• astronomical body
• Astronomical Camera
• astronomical eyepiece
• film-stress interferometer
• film strip
• film supply
• film tansporting system
• film thickness
• film thickness gauge
• film thickness measuring
• film thickness measuring device
• film thickness meter
• film thickness monitor
• film velocity